The instant he saw that glass bottle, Fenrir Greyback's eyes flew wide, and his body arched on instinct, the shackles binding his neck and limbs clattering again and again.
He screamed in terror, "What are you doing?"
That scream was absolutely his true feelings, not some "false show" meant to hide his own secret.
After so many experiments, he now had a rough understanding of Vizet's magical level.
Even if he could not stand shoulder to shoulder with Voldemort, he had at least reached the level of a Hogwarts professor, and a professor of magical subjects like Transfiguration or Charms Class at that.
The most terrifying part was that what Vizet had that matched a Hogwarts professor was not the level of some single magical subject, but the level of most magical subjects.
As for why he had such an understanding, it was probably because he had gone through far too many experiments.
The types of these experiments included nearly every magical subject he knew of, and even magical subjects he did not understand very well.
He could only judge from his own experience that Vizet must have combined several magical subjects to conceive such a terrifying experimental procedure.
Being able to fuse multiple magical subjects together and attempt them in a single experiment was already enough to show Vizet's magical level.
Fenrir Greyback knew what Vizet was holding. It was a Memory Thread, and according to past practice, the final destination of this Memory Thread would definitely be his head.
If this had been in the past, it was not as if he had never experienced such an experiment before.
But the situation now was very different. He could see "himself transformed into a Werewolf" in his dreams, and he had already begun fusing with that "self transformed into